We are attempting to use dynamic keywords in my app and some of them have spaces. The MoPub documentation states that spaces are allowed.

Passing Keywords
Keywords allow you to target certain ad requests with user data. This feature is often used to differentiate a specific user demographic or users on different app versions.

For banner and interstitial ads, pass the keywords from your app to MoPub as a comma-separated list in the ad view. They should be formatted as key/value pairs (e.g. m_age:24). You can use any character except “&” and “=”. Spaces are allowed, and special characters are discouraged.

Here are the log files from XCode simulator that show what we are passing into MoPub

Question:
What delimiter should we use to allow spaces to work in my target keywords?

By the way:
Unfortunately, we only tested against single word keywords and missed keywords with spaces in pre-release testing. The app is currently in production and can not be easily changed out. So stripping out the spaces of the dynamic due to the apple store release delays. We support time sensitive events, so time is of the essence.